roughness in cylinder 1 P38 thor engine but no fault code??!!!, diagnostic screenshot..

Suddenly my pet develop vibration and rotten egg smell from the pipe. after checking and replacing the spark and HT wire on the cylinder 1, nothing change... I keep the roughness
in cylinder 1 and NO FAULT CODE. do not know what to do..

here is the diagnostic screenshot





please advice.

Thanks

Do all the plugs look the same colour?
It could still be a bad plug or lead.
You never get 100% firing on every cylinder every time, that's normal. There's a rolling threshold before it trips a misfire code. 5 isn't ideal but it's not really bad.
Have you done a compression test?

kermit_rr said:

Do all the plugs look the same colour?
It could still be a bad plug or lead.
You never get 100% firing on every cylinder every time, that's normal. There's a rolling threshold before it trips a misfire code. 5 isn't ideal but it's not really bad.
Have you done a compression test?

Click to expand...

level 5 for roughness on cylinder 1 is at idle. the engine vibration and rotten egg smell is strongly felt in the cabin when driving.

I have no fault regarding the injectors?..., and the plug (picture attached) removed from the cylinder 1 was corroded on the wire side but not wet despite the rotten egg smell...

4 month ago, I got rotten egg smell as well when my cylinder 4 misfired, at this time, the plug has full of crap and misfire FAULT appeared. after I changed the plug, everything was fine and no more rotten egg smell.in fact when there is a misfire, unburnt fuel goes in the catalyzer and produce the rotten egg smell.

BUT THIS TIME, even after replacing the spark and HT wire on the cylinder 1, the violent vibration and the roughness do not disappear at all .NO FAULT or misfire is detected by the ecu....
it is like a misfire behavior undetected by the ecu....

the cylinder 1 seems to be the most affected by the roughness according to the diagnostic test.
by the way is it possible that the problem is not from the cylinder 1 but from an other one??
on the first diagnostic screenshot the cylinder 8 have a some roughness as well..., I am wondering if the cylinder 1 and 8 are synchronized or related together?.

no, 1 and 8 are not on the same coil.
roughness is a rolling misfire count. each increase is an actual misfire, but this doesnt count as an actual misfire event until you have a certain number per minute. i think roughness has to reach ~10, if i recall correctly
however, the firing order is 1-8-4-3-6-5-7-2 so if 1 and 8 have more misfires than the rest then this might be something you feel.
you can measure the resistance of your plug leads, make sure it doesnt spike as you wiggle each end.
from the manual;
This (roughness) value will increase the more unevenly the engine is running. Engine roughness is not displayed if idle.
When the ECU detects a possible misfire, this count value is increased by one. If the value increases to more than
a preset limit within 1000 engine revolutions, a misfire fault is set. If not, the misfire count value will be cleared to 0 and a new count begins. It is normal to expect a certain number of 'false' misfire detections during each count.

that said, if the coil, leads and plug are good then you're left with either a valve problem or cam wear

the coil is good because you dont have corresponding roughness on #5 or #6 - wasted spark system

kermit_rr said:

no, 1 and 8 are not on the same coil.
roughness is a rolling misfire count. each increase is an actual misfire, but this doesnt count as an actual misfire event until you have a certain number per minute. i think roughness has to reach ~10, if i recall correctly
however, the firing order is 1-8-4-3-6-5-7-2 so if 1 and 8 have more misfires than the rest then this might be something you feel.
you can measure the resistance of your plug leads, make sure it doesnt spike as you wiggle each end.
from the manual;
This (roughness) value will increase the more unevenly the engine is running. Engine roughness is not displayed if idle.
When the ECU detects a possible misfire, this count value is increased by one. If the value increases to more than
a preset limit within 1000 engine revolutions, a misfire fault is set. If not, the misfire count value will be cleared to 0 and a new count begins. It is normal to expect a certain number of 'false' misfire detections during each count.

that said, if the coil, leads and plug are good then you're left with either a valve problem or cam wear

the coil is good because you dont have corresponding roughness on #5 or #6 - wasted spark system

Click to expand...

right now i'd be checking and rechecking the plugs and the leads because its occasional

It needs old fashioned engine basics rather the repeated diagnostics, i.e.

1. Clean or better still replace spark plugs
2. Test injector spray pattern & clean them. It's easy DIY using a kit like this https://ebay.us/m/cNgk6I
3. Compression check all cylinders (with spark plugs removed)
4. Fuel rail pressure (just need a tyre gauge on the test valve)

None of these will log specific faults in the ECU, but just symptoms like you are seeing.

As others have said on RR.net, bad egg smell is probably the CAT's. The fuelling figures look about right.

As said it's a wasted spark system, it will spark down 2 leads at the same time. Normally when a coil goes it will impact both cylinders not one.
I would suggest the coil is working fine at this point.

It could be a dodgy injector, but i would say not likely. Yet.

Move the plug to a different cylinder.

Move the plug lead or replace with another of the same length

Do a compression test

Does it get better/worse/same under load?